Monitoring subsidence rates along road network by persistent scatterer SAR interferometry with high-resolution TerraSAR-X imagery

Ground subsidence is one of the key factors damaging transportation facilities, e.g., road networks consisting of highways and railways. In this paper, we propose to apply the persistent scatterer synthetic aperture radar interferometry （PS-InSAR） approach that uses high- resolution TerraSAR-X （TSX） imagery to extract the regional scale subsidence rates （i.e., average annual sub- sidence in mm/year） along road networks. The primary procedures involve interferometric pair selection, interfer- ogram generation, persistent scatterer （PS） detection, PS networking, phase parameterization, and subsidence rate estimation. The Xiqing District in southwest Tianjin （China） is selected as the study area. This district contains one railway line and several highway lines. A total of 15 TSX images covering this area between April 2009 and June 2010 are utilized to obtain the subsidence rates by using the PS-InSAR （PSI） approach. The subsidence rates derived from PSI range from -68.7 to -1.3 mm/year. These findings show a significantly uneven subsidence pattern along the road network. Comparison between the PSI-derived subsidence rates and the leveling data obtained along the highways shows that the mean and standard deviation （SD） of the discrepancies between the two types of subsidence rates are 0.1 and 4-3.2 mm/year, respectively. The results indicate that the high-resolution TSX PSI is capable of providing comprehensive and detailed subsidence information regarding road networks with millimeter-level accuracy. Further inspections under geo- logical conditions and land-use categories in the study area indicate that the observed subsidence is highly related to aquifer compression due to groundwater pumping. Therefore, measures should be taken to mitigate groundwater extraction for the study area.

Land Subsidence in Xiong’an New Area,China Revealed by InSAR Observations

In 2017,China’s central government approved the national strategy to build Xiong’an New Area(XNA,100 km southwest to Beijing),which was announced as a"millennium strategy"and a"demo area"for a sustainable,modern,and innovative urban model.Xiong’an will draw in as much as$380 billion investment and is expected to help accelerate the development of the wider Beijing-Tianjin-Hebei(Jingjinji)Area.In this paper,present subsidence in the XNA area is investigated using InSAR observations for the first time.The 24 SAR images acquired by European Space Agency’s Sentinel-1 satellites during the period from June 2017 to July 2018 suggest that in the north of Xiong County,the subsidence rate reaches up to 90 mm/y,which is highly correlated with the exploitation of geothermal drilling.As the construction in the XNA area will significantly accelerate and its high-quality development,the InSAR findings could provide valuable information for future sustainable urban planning and underground infrastructure construction.

Generalized modeling and experimental research on the transient response of supercapacitors under compressive mechanical loads

Supercapacitors(SCs)have been successfully used in electric vehicles or military equipment systems for their high power density.However,the mechanical impacts from vehicle crashes and missile penetration probably cause performance fluctuations or failure of SCs,which may threaten the safety of systems using SCs.In this paper,a generalized circuit model to analyze the transient process of SCs under mechanical loads is proposed.The circuit model simultaneously takes capacitance change,internal short-circuit and resistance change into account,an extra resistor-capacitor circuit(RCC)is added to simulate the nonlinear behavior during charging and discharging.Subsequently,the relationships between pressure and fundamental circuit parameters are determined by static methods.By taking the static test data into the circuit model,the transient response of different types of SCs under particular mechanical loading conditions is predicted.Finally,the influences of some crucial parameters on the voltage responses of SCs are revealed based on the simulations,which provide references for designing and optimizing mechanical load-resistant or self-sensing SCs in specific application scenarios.

Dynamic transfer model and applications of a penetrating projectile‐fuze multibody system

In modern warfare,fortifications are being placed deeper underground and with increased mechanical strength,placing higher demands on the target speed of the penetrating munitions that attack them.In such practical scenarios,penetrating fuze inevitably experience extreme mechanical loads with long pulse durations and high shock strengths.Experimental results indicate that their shock accelerations can even exceed those of the projectile by several times.However,due to the unclear understanding of the dynamic transfer mechanism of the penetrating fuze system under such extreme mechanical conditions,there is still a lack of effective methods to accurately estimate and design protection against the impact loads on the penetrating fuze.This paper focuses on the dynamic response of penetrating munitions and fuzes under high impact,establishing a nonlinear dynamic transfer model for penetrating fuze systems,which can calculate the sensor overload signal of the fuze location.The results show that the relative error between the peak acceleration obtained by the proposed multibody dynamic transfer model and that obtained by experimental tests is only 15.7%,which is much lower than the 26.4%error between finite element simulations and experimental tests.The computational burden of the proposed method mainly lies in the parameter calibration process,which needs to be performed only once for a specific projectile‐fuze system.Once calibrated,the model can rapidly conduct parameter scanning simulations for the projectile mass,target plate strength,and impact velocity with an extremely low computational cost to obtain the response characteristics of the projectile‐fuze system under various operating conditions.This greatly facilitates the practical engineering design of penetrating ammunition fuze.

Simulation and structure optimization of triboelectric nanogenerators considering the effects of parasitic capacitance

Parasitic capacitance is an unavoidable and usually unwanted capacitance that exists in electric circuits, and it is the most important second-order non-ideal effect that must be considered while designing a triboelectric nanogenerator （TENG） because its magnitude is comparable to the magnitude of the TENG capacitance. This paper investigates the structure and performance optimization of TENGs through modeling and simulation, taking the parasitic capacitance into account. Parasitic capacitance is generally found to cause severe performance degradation in TENGs, and its effects on the optimum matching resistance, maximum output power, and structural figures-of-merit （FOMs） of TENGs are thoroughly investigated and discussed. Optimum values of important structural parameters such as the gap and electrode length are determined for the different working modes of TENGs, systematically demonstrating how these optimum structural parameters change as functions of the parasitic capacitance. Additionally, it is demonstrated that the parasitic capacitance can improve the height tolerance of the metal freestanding-mode TENGs. This work provides a theoretical foundation for the structure and performance optimization of TENGs for practical applications and promotes the development of mechanical energy-harvesting techniques.

Double-kill contribution of high-roughness high-density porous carbon electrodes to mechanically self-sensing supercapacitors

Impact detecting and counting are fundamental functions of fuses used in hard target penetration weapons.However,detection failure caused by battery breakdown in high-g acceleration environments poses a vulnerability for such weapons.This paper introduces a novel supercapacitor that combines energy storage and high-g impact detection,called self-sensing supercapacitor.By deliberately inducing a transient soft short-circuit during shock in the supercapacitor,it is possible to detect external impact by its transient voltage drop.To realize this concept,firstly,by introducing the contact theory and force-induced percolation model,the electrode strength and roughness are found to have key impacts on the formation of soft circuits.Subsequently,to meet the needs for sensitivity and capacity,a high-density porous carbon(HDPC)that combines high mechanical strength and porosity,is selected as a suitable candidate based on the analysis results.Furthermore,a two-step curing method is proposed to prepare the high-roughness HDPC(HRHDPC)electrode and to assemble the self-sensing supercapacitor.Due to the rich specific surface of the electrodes and the high surface strength and roughness conducive to the formation of transient soft short circuits,the self-sensing supercapacitor not only possesses an excellent specific capacitance(171 F/g at 0.5 A/g)but also generates significant voltage response signals when subjected to high-g impacts ranging from 8000g to 31,000g.Finally,the self-sensing supercapacitor is applied to compose a successive high-g impact counting system and compared to traditional solutions(sensors and tantalum capacitors)in the military fuzes.The results show that the self-sensing supercapacitor-based system exhibits advantages in terms of size,power consumption,and counting accuracy.